Combine the base ingredients: Place chicken breasts, chicken broth, heavy cream, garlic, onion, Italian seasoning, salt, and pepper in the crockpot. Stir gently to combine before covering with the lid.
Cook on low or high: Set the slow cooker to low for 6 hours or high for 3 hours. The chicken is ready when it reaches 165°F and shreds easily with a fork.
Remove and shred the chicken: Lift the chicken breasts onto a cutting board and shred them into bite-size pieces using two forks. Return the shredded chicken to the crockpot and stir into the broth.
Add the lasagna noodles: Break the lasagna noodles into 1-2 inch pieces and drop them into the hot broth. Switch the crockpot to high if it isn't already.
Simmer until noodles soften: Cook the noodles in the broth for 20-25 minutes, stirring once halfway through, until tender but not falling apart.
Lower the heat before adding cheese: Turn the crockpot to low or off completely so the broth isn't boiling. This keeps the cheese from turning grainy when it's stirred in.
Stir in mozzarella and parmesan: Add the mozzarella and parmesan to the broth in handfuls, stirring after each addition until fully melted and the broth turns glossy.
Taste and adjust seasoning: Taste the broth and add more salt, pepper, or Italian seasoning if needed. The cheese adds saltiness, so adjust gradually.
Ladle into bowls: Spoon the hot soup into bowls, making sure each serving gets plenty of chicken and noodles.
Top with ricotta and garnish: Add a spoonful of ricotta cheese to the center of each bowl and sprinkle with chopped parsley if desired before serving.